Regular walking and other aerobic exercise can not guarantee a longer lifespan, but it improves the chances.
Mr. Montgomery told me that he came into this world when his daddy came home from the Civil War, married his hometown sweetheart, and started a family. I knew him when he was in his nineties and I was a teenager. He was the old man up the street.
He used to take daily walks. Even as a nonagenarian he said that he tried to walk a mile a day. He wasn't quite as fast the young folks in the neighborhood, but he kept walking. I don't remember how old he was when he died, but he was probably in his upper nineties.
One example does of course not prove anything, and most of us can think of examples of people who had all the wrong habits and still managed to live to similar old ages. His daily walks however probably contributed to his longevity.
Regular aerobic exercise along with other contributing factors such as good diet, genetics, and so forth will improve one's chances of a long lifespan. Regular walking or other exercise will not however guarantee a long life, just as bad health habits will not guarantee a short life. The best we can do is improve the odds.
Mr. Montgomery's regular walks were not the only factor contributing to his long life, but they improved the odds for him enough that he lasted nearly a century.
